It is proposed to investigate the effects of arabinosyl cytosine and 5-aza-cytidine on the synthesis and/or turnover of the phospholipid, sialoglycolipid, and sialoglycoprotein components of P388 leukemic cells and the manifestation of these effects at the membrane level with a view toward delineating the action mechanisms of these antineoplastic agents. The site(s) of action of the drugs on the formation and/or metabolism of the CTP-activated intermediates of phospholipid, sialoglycolipid and sialoglycoprotein synthesis will be determined both in vivo, by analysis of radiolabeled precursor incorporation into specific phospholipids and sialylated compounds, and in vitro, by analysis of the activities of the CTP-dependent enzymes. For the specific enzymes affected by ara-C and/or 5-aza-C, the mode(s) of action of the drugs will be characterized by in vitro assays designed to measure the effectiveness of ara-C and 5-aza-C analogs as substrates and/or inhibitors of the enzymatic activities. The extent to which the effects of ara-C and 5-aza-C on the synthesis and/or turnover of these membrane components are manifested at the membrane level will be examined by compositional analysis of the subcellular organelles biochemically and cytochemically. Specific effects on membrane synthesis and assembly will be examined by analysis of the subcellular distribution of these enzymes biochemically and cytochemically and by autoradiographic analysis using precursors specific for phospholipids and sialic acid. The relevance of these effects to the antineoplastic actions of the drugs will then be determined.